Some vehicles are configured to operate in an autonomous mode in which the vehicle navigates through an environment with little or no input from a driver. Such a vehicle may include one or more sensors that are configured to sense information about the environment. The vehicle may use the sensed information to navigate through the environment.
For example, if an output of the sensors is indicative that the vehicle is approaching an obstacle, the vehicle may navigate around the obstacle. Additionally, a vehicle may sense information about traffic signs and traffic signals. Traffic signs may provide regulatory information or warning information while traffic signals positioned at road intersections, pedestrian crossings, and other locations may be used to control competing flows of traffic. In an instance in which a map of known locations of traffic controls is available, a vehicle may be prompted to locate a traffic control and respond accordingly. Other types of vehicles may also rely on information about the presence and behavior of traffic controls in an area. For example, mapping applications may utilize a map of known locations of traffic controls to determine driving directions for a vehicle. As another example, driver assistance systems may alert drivers about the presence of a traffic control when their vehicle is approaching a location of the traffic control. Other examples are also possible.